Transglycosylation reactions of Bacillus stearothermophilus maltogenic amylase with acarbose and various acceptors

It was observed that Bacillus stearothermophilus maltogenic amylase cleaved the first glycosidic bond of acarbose to produce glucose and a pseudotrisa ccharide (PTS) that was transferred to C-6 of the glucose to give an alpha- (1 --> 6) glycosidic linkage and the formation of isoacarbose. The addition of a number of different carbohydrates to the digest gave transfer product s in which PTS was primarily attached alpha-(1 --> 6) to D-glucose, D-manno se, D-galactose, and methyl alpha-D-glucopyranoside. With D-fructopyranose and D-xylopyranose, PTS was linked alpha-(1 --> 5) and alpha-(1--> 4), resp ectively. PTS was primarily transferred to C-6 of the nonreducing residue o f maltose, cellobiose, lactose, and gentiobiose. Lesser amounts of alpha-(1 --> 3) and/or alpha-(1 --> 4) transfer products were also observed for the se carbohydrate accepters. The major transfer product to sucrose gave PTS l inked alpha-(1 --> 4) to the glucose residue. alpha,alpha-Trehalose gave tw o major products with PTS linked alpha-(1 --> 6) and alpha-(1 --> 4). Malti tol gave two major products with PTS linked alpha-(1 --> 6) and alpha-(1 -- > 4) to the glucopyranose residue. Raffinose gave two major products with P TS linked alpha-(1 --> 6) and alpha-(1 --> 4) to the D-galactopyranose resi due. Maltotriose gave two major products with PTS linked alpha-(1 --> 6) an d alpha-(1 --> 4) to the nonreducing end glucopyranose residue. Xylitol gav e PTS linked alpha-(1 --> 5) as the major product and D-glucitol gave PTS l inked alpha-(1 --> 6) as the only product. The structures of the transfer p roducts were determined using thin-layer chromatography, high-performance i on chromatography, enzyme hydrolysis, methylation analysis and C-13 NMR spe ctroscopy. The best acceptor was gentiobiose, followed closely by maltose a nd cellobiose, and the weakest acceptor was D-glucitol. (C) 1998 Elsevier S cience Ltd. All rights reserved.